This invention concerns substituted benzo pentathiepins, intermediate 1,2,3-benzothiadiazoles and the process for making the former by reacting the latter with elemental sulfur.
Unsubstituted benzopentathiepin is known (Feher et al., Z. Anorg. Allg. Chem., 452, 37 to 42 (1979); Feher et al., Tet. Lett., 2125 to 2126 (1971). It is prepared from 1,2-benzenedithiol and S.sub.3 Cl.sub.2. No utility is described. Feher et al., in Z. Naturforsch. B, 27, 1006 (1972), describe preparation of the 7,8-dimethyl derivative by a similar method.
A reduced hexahydrobenzopentathiepin was prepared by Feher et al., according to the method of Feher et al. described above: Angew. Chem. Int. Ed., 6, 703 (1967). Nametkin et al., in Izv. Akad. Nauk. SSSR, Ser. Khim., 12, 2841 (1980), describe a method for making said reduced pentathiepins by use of an organoiron complex.
Watkins et al., J. Het. Chem., 19, 459 to 462 (1982) describe the x-ray crystal structure of a complex indene pentathiepin. Synthesis and utility are not described.
A variety of heterocyclic pentathiepins are known. For instance, U.S. Pat. No. 4,094,985 describes the following as fungicides: ##STR1## where X is CN or ##STR2## et cetera. U.S. Pat. No. 4,275,073 describes these pyrazolopentathiepins as fungicides: ##STR3## where R=H, C.sub.1 -C.sub.6 alkyl, C.sub.5 -C.sub.6 cycloalkyl, --CH.sub.2 O, --Ar. Both of the patents describe processes employing a thiol or dithiol and S.sub.2 Cl.sub.2. The substituted benzopentathiepins of this invention cannot be made by literature techniques.
Certain 1,2,3-benzothiadiazoles are known, their syntheses being reviewed by Kurzer in "Org. Cmpd. of Sulphur, Selenium, Tellurium", Royal Society of Chemistry, London, Vols. 1 to 6 (1970 to 1980). A typical synthesis is diazotization of an o-aminobenzenethiol as follows: ##STR4##
In Oae, "Organic Chemistry of Sulfur", at pages 346 to 348, Plenum Press, N.Y. (1977), are reviewed the various means of reducing disulfides to give thiols. Reagents for these reductions include sodium borohydride, lithium aluminum hydride, sodium amalgam, zinc or tin with aqueous acid, phosphines and phosphites.
Cairns et al., J. Am. Chem. Soc., 74, 3982 to 3989 (1952), describe the reduction of a linear tetrasulfide by lithium aluminum hydride. There is no known art, however, that describes reduction of a pentathiepin to give a dithiol.
The 1,2-benzenedithiols can be prepared by pyrolysis of benzothiadiazoles in the presence of carbon disulfide and alkaline hydrolysis of the intermediate trithiocarbonate: Hunig et al., Liebigs Ann. Chem.. 738, 192 to 194 (1970). The process requires a pressure vessel and temperatures of 220.degree. C.